6n9f | pdb_00006n9f
Crystal structure of the Thermus thermophilus 70S ribosome in complex with a short substrate mimic ACCA-DPhe and bound to mRNA and P-site tRNA at 3.7A resolution
Structural highlights
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Function[RL25_THET2] This is one of the proteins that binds to the 5S RNA in the ribosome where it forms part of the central protuberance (By similarity). [RL31_THET2] Binds the 23S rRNA (By similarity). [RS13_THET2] Located at the top of the head of the 30S subunit, it contacts several helices of the 16S rRNA. In the 70S ribosome it contacts the 23S rRNA (bridge B1a) and protein L5 of the 50S subunit (bridge B1b), connecting the 2 subunits; these bridges are implicated in subunit movement. Contacts the tRNAs in the A and P-sites (By similarity). [RL32_THET8] Found on the solvent side of the large subunit.[HAMAP-Rule:MF_00340] [RS9_THET8] Part of the top of the head of the 30S subunit. The C-terminal region penetrates the head emerging in the P-site where it contacts tRNA.[HAMAP-Rule:MF_00532_B] [RL24_THETH] One of two assembly initiator proteins, it binds directly to the 5'-end of the 23S rRNA, where it nucleates assembly of the 50S subunit. One of the proteins that surrounds the polypeptide exit tunnel on the outside of the subunit. [RS18_THET2] Binds as a heterodimer with protein S6 to the central domain of the 16S rRNA, where it helps stabilize the platform of the 30S subunit (By similarity). [RS17_THET8] One of the primary rRNA binding proteins, it binds directly to 16S rRNA where it helps nucleate assembly of the platform and body of the 30S subunit by bringing together and stabilizing interactions between several different RNA helices. The combined cluster of proteins S8, S12 and S17 appears to hold together the shoulder and platform of the 30S subunit.[HAMAP-Rule:MF_01345] Deletion of the protein leads to an increased generation time and a temperature-sensitive phenotype.[HAMAP-Rule:MF_01345] [RS11_THET2] Located on the upper part of the platform of the 30S subunit, where it bridges several disparate RNA helices of the 16S rRNA. Forms part of the Shine-Dalgarno cleft in the 70S ribosome (By similarity). [RL27_THET8] Found on the solvent side of the large subunit.[HAMAP-Rule:MF_00539] [RS15_THETH] One of the primary rRNA binding proteins, it binds directly to 16S rRNA where it helps nucleate assembly of the platform of the 30S subunit by binding and bridging several RNA helices of the 16S rRNA. Forms an intersubunit bridge (bridge B4) with the 23S rRNA of the 50S subunit in the ribosome (By similarity). [RL34_THET8] Found on the solvent side of the large subunit.[HAMAP-Rule:MF_00391] [RS10_THETH] Involved in the binding of tRNA to the ribosomes (By similarity). [RS16_THET2] Binds to the lower part of the body of the 30S subunit, where it stabilizes two of its domains (By similarity). [RSHX_THETH] Binds at the top of the head of the 30S subunit. It stabilizes a number of different RNA elements and thus is important for subunit structure (By similarity). [RS14Z_THETH] Binds 16S rRNA, required for the assembly of 30S particles and may also be responsible for determining the conformation of the 16S rRNA at the A site (By similarity). [RS12_THETH] With S4 and S5 plays an important role in translational accuracy (By similarity).[HAMAP-Rule:MF_00403_B] Interacts with and stabilizes bases of the 16S rRNA that are involved in tRNA selection in the A site and with the mRNA backbone. Located at the interface of the 30S and 50S subunits, it traverses the body of the 30S subunit contacting proteins on the other side and probably holding the rRNA structure together. The combined cluster of proteins S8, S12 and S17 appears to hold together the shoulder and platform of the 30S subunit (By similarity).[HAMAP-Rule:MF_00403_B] Publication Abstract from PubMedDuring protein synthesis, ribosomes discriminate chirality of amino acids and prevent incorporation of D-amino acids into nascent proteins by slowing down the rate of peptide bond formation. Despite this phenomenon being known for nearly forty years, no structures have ever been reported that would explain the poor reactivity of D-amino acids. Here we report a 3.7A-resolution crystal structure of a bacterial ribosome in complex with a D-aminoacyl-tRNA analog bound to the A site. Although at this resolution we could not observe individual chemical groups, we could unambiguously define the positions of the D-amino acid side chain and the amino group based on chemical restraints. The structure reveals that similarly to L-amino acids, the D-amino acid binds the ribosome by inserting its side chain into the ribosomal A-site cleft. This binding mode does not allow optimal nucleophilic attack of the peptidyl-tRNA by the reactive alpha-amino group of a D-amino acid. Also, our structure suggests that the D-amino acid cannot participate in hydrogen-bonding with the P-site tRNA that is required for the efficient proton transfer during peptide bond formation. Overall, our work provides the first mechanistic insight into the ancient mechanism that helps living cells ensure the stereochemistry of protein synthesis. Mechanistic insights into the slow peptide bond formation with D-amino acids in the ribosomal active site.,Melnikov SV, Khabibullina NF, Mairhofer E, Vargas-Rodriguez O, Reynolds NM, Micura R, Soll D, Polikanov YS Nucleic Acids Res. 2018 Dec 6. pii: 5231803. doi: 10.1093/nar/gky1211. PMID:30520988[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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